1. Field of the Invention
The present invention relates to a transmission type screen.
2. Related Art
A transmission type screen for use as a rear-projection screen has a configuration in which a front plate for protecting lenses, a lenticular lens and a fresnel lens are layered one after another in this order from the side of viewers in general.
By the way, the fresnel lens and the lenticular lens are disposed in very close proximity such that the projecting edges of the fresnel lens almost contact with the lenticular lens, or in contact. It is because the larger the gap between the fresnel lens and the lenticular lens, the more light deviates from the position where it is desired to pass, thus loosing the high precision optical characteristics, e.g., the high resolution, due to refraction of the light transmitting from the fresnel lens to the gap and transmitting from the gap to the lenticular lens.
However, this configuration may cause blur partially in the outer peripheral part of the screen in particular when the fresnel lens is made of synthetic resin because the projecting edges of the fresnel lens are slightly crushed and deformed when they contact with and are pressed by the lenticular lens, increasing the density of the part where the fresnel lens contacts with the lenticular lens.
Still more, because lens portions of the fresnel lens A and lens portions of the lenticular lens B are arranged in parallel with a predetermined pitch width and have a periodic structure as shown in FIG. 1, they interfere each other, causing Moire that hampers normal appreciation of images with a period of least common multiple of their pitch widths.
Accordingly, it is an object of the invention to solve the above-mentioned problems by providing a very practical transmission type screen that enables viewers to appreciate good images without having conspicuous blur and Moire by preventing the blur from occurring on the screen as much as possible by contacting portions of the fresnel lens with the lenticular lens at an adequate intervals and by reducing the intensity of Moire caused by the periodic structure of the fresnel lens and the directional light scattering lens, e.g., the lenticular lens, as much as possible.
This object may be achieved through the combination of features described in an independent claim of the invention. Dependent claims thereof specify preferable embodiments of the invention.